Papers obtained under the Freedom of Information Act show that on five occasions since 2004 private firms with police contracts have successfully applied to use the database to help them develop computer programs.

The DNA database contains records of 4.2 million people, of which a million have never been convicted of an offence. Records are rarely deleted, even if a person is not charged.

The disclosure comes ahead of a hard-hitting report from the Government’s genetics watchdog next week which will call for more safeguards on how the database is run.

(Article continues below)

Ministers say the database is a crucial tool in solving crimes. But when it was set up, there was no suggestion that profiles would be made available to private businesses for commercial purposes.

The companies involved were not given the identities of the people whose DNA profiles they analysed and used them for research that could be useful to the police. But critics said it was unacceptable that profiles had been handed over secretly without any public debate or the consent of those concerned.

The Liberal Democrats said that the “highly dubious ethical practice of dishing DNA out for research must be suspended immediately”. Jenny Willott, the MP who obtained the information, said: “It is appalling that these Big Brother practices have been allowed to go on unchecked for so long and with extremely limited ethical standards.”

The newly disclosed documents show that since 1999 the Government has received 45 requests for thousands of profiles from the DNA data-base and granted access on 25 occasions.